[PATCH 3/3] drm/i915: Fix gt reset with GuC submission disabled

[Nirmoy Das <nirmoy.das@xxxxxxxxx>]

Currently intel_gt_reset() happens as follows:

reset_prepare() ---> Sends GDRST to GuC, GuC is in GS_MIA_IN_RESET
do_reset()
  intel_gt_reset_all_engines()
    *_engine_reset_prepare() -->RESET_CTL expects running GuC
    *_reset_engines()
intel_gt_init_hw() --> GuC comes out of GS_MIA_IN_RESET with FW loaded.

Fix the issue by sanitizing the GuC only after resetting requested
engines and before intel_gt_init_hw().

Note intel_uc_reset_finish() and intel_uc_reset() are nop when
guc submission is disabled.

Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/intel_reset.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
index 6504e8ba9c58..bd166f5aca4b 100644
--- a/drivers/gpu/drm/i915/gt/intel_reset.c
+++ b/drivers/gpu/drm/i915/gt/intel_reset.c
@@ -907,8 +907,17 @@ static intel_engine_mask_t reset_prepare(struct intel_gt *gt)
 	intel_engine_mask_t awake = 0;
 	enum intel_engine_id id;
 
-	/* For GuC mode, ensure submission is disabled before stopping ring */
-	intel_uc_reset_prepare(&gt->uc);
+	/**
+	 * For GuC mode with submission enabled, ensure submission
+	 * is disabled before stopping ring.
+	 *
+	 * For GuC mode with submission disabled, ensure that GuC is not
+	 * sanitized, do that at the end in reset_finish(). reset_prepare()
+	 * is followed by engine reset which in this mode requires GuC to
+	 * be functional to process engine reset events.
+	 */
+	if (intel_uc_uses_guc_submission(&gt->uc))
+		intel_uc_reset_prepare(&gt->uc);
 
 	for_each_engine(engine, gt, id) {
 		if (intel_engine_pm_get_if_awake(engine))
@@ -1255,6 +1264,9 @@ void intel_gt_reset(struct intel_gt *gt,
 
 	intel_overlay_reset(gt->i915);
 
+	/* sanitize uC after engine reset */
+	if (!intel_uc_uses_guc_submission(&gt->uc))
+		intel_uc_reset_prepare(&gt->uc);
 	/*
 	 * Next we need to restore the context, but we don't use those
 	 * yet either...
-- 
2.42.0